Transformer cut-out



Oct. 15, 1929- R. w. SHOEMAKER TRANSFORMER CUT-OUT Filed May 1 1933INVENTOR R .WSIJ oemvnker BY Q4.)

ATTORNE INSULATION Patented Oct. 15, 1929 PATENT OFFICE RICHARD W.SHOEMAKEB, OF TURLOCK, CALIFORNIA TRANSFORMER cur-our Application filedMay 12,

This invention relates to devices for protecting transformers such asare interposed in power linesbetween the main source of current and thepoint of consumption to prevent damage to the transformer in the eventof an overload clue to short circuit or other cause being had in theline beyond the transformer or atthe point of consumption.

At present the protecting means used for this purpose is in the form ofordinary fuses, which are a. source of annoyance to power companies, asthey blow out immediately upon the occurence of any trouble or overloadsin any line supplied by the transformer,

5 no matter how momentary or short-lived this overload may be. Undersuch operating conditions, therefore, all users of current beyond thetransformer or taking from the same are deprived of current until thefuses are replaced, even though the trouble itself is only in one line.

The principal object of my invention, therefore, is to avoid the aboveobjectionable feature by providing a protective cut-out structure soarranged that the circuit to the transformer will not be broken untilthe overload has continued for a certain length of time, both the amountof overload and the duration of time being adjustable for each 0application as momentary overloads within reasonable limits are notinjurious to a transformer. It is my invention that this cut-outstructurewill not operate until the overload has existed for asufficient len th of time to endanger the transformer, an in the eventthat the overload ceases before such injurious time period has occured,then the cut-out structure will not function and will remain insubstantially the same condition as it was 4 before the application ofsaid momentary overload, which may have ceased to exist either by the oeration of individual fuses further remove from the transformer, or by achange in load conditions.

lrVith my improved cut-out structure, therefore, the transformer circuitwill be only broken under extreme conditions which are not very likelyto be had in ordinary service, while at the same time the cut-outstructure functions before any harm can be done 1928. Serial R0.277,212.

to the transformer due to the overloaded conditions.

A further object of the invention is to provide a device for the purposeso constructed that the functioning of the device, when breaking thetransformer circuit only requires the eplacing of a single small elementto again cause the circuit to be closed and conditions to be renderednormal; This element may be inserted very easily and quickly and itscost is negligible compared to that of the complete fuses ordinarilyused and which when once blown must be entirely replaced.

Still another object is to provide a structure for the purpose of such anature that the amount of overload and the duration of time it will becarried before the circuit is broken, can be altered to suit differentconditions.

A further object of the invention is to roduce a simple and inexpensivedevice an yet one which will be exceedingly effective for the urpose forwhich it is designed.

T iese objects I accomplish by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claims.

In the drawings similar characters of reference indicate correspondingparts in the several views:

Fig. 1 is a plan view of my improved cutout structure.

Fig. 2 is a side elevation of the same.

F Fig. 3is a cross section on the line 3-3 of ig. 1. Fig. 4 is a diagramofa transformer and its circuit as connected with my cut-out device.

Fig. 5 is a side elevation of a modified form are'adapted to be bridgedand engaged by contact plates 5 which are mounted on stems that thesprings are then under a certain compression.

-The bar is thus normally held so as to maintain the contacts 2 engagedby the plates 5 by the following means: mounted on the panel between thepairs of contacts is a rigid metal block 10 ofiron or the like whichintermediate its ends has a circular socket 11 open to the top of theblock. The block is preferably ribbed as shown so as to provide a heatradiating surface of suflicient area to prevent the block from heatingtoo rapidly and to too great an extent. Removably seated in and closelyfitting the socket is a plug 12 of very soft metal alloy of specialcharacter. 4 This plug preferably has a melting point approximately 200F., though such point may be altered by altering the composition of thealloy to harden or soften the same somewhat. A hard metal stem 13 isconnected to the plug and projects upwardly through the bar 7, this stemhaving adjustable nuts 14 thereon above the bar and engaging the same.The block is provided with a removable cover plate 15 having an orifice16 about the stem 13 WhlCh is concentric with bpt somewhat smaller thanthe socket and p ug. Extending under the block between the same and thepanel and insulated from the block and from each other are transverselyspaced heating or resistance elements 17 of suitable character, which atone end are connected to separated binding posts 18,0n the panel and atthe other end are connected in common to a single binding post 19.

The cut-out device is particularly adapted to'be mounted in connectionwith a transformer T such as used to transform current from high.voltage ower lines to 110 V. or 220 V.; or to 220 or 440 V. dependingon the capacity of the transformer used. Standard transformers are madeso that any one may be conned'ted to supply either one of the twocorelated voltages; but special six- !ead transformers are also made soas to be connected to supply eit'er 110 V., 220 V., or 440 V. as may bedesired. In such a case, the primary winding 20 of the transformer isconnected to the power lines 21, while the secondary windings 22 of thetransformer are connected at their opposite ends to the terminal posts3, and at their adjacent ends to the binding posts 18 of the resistanceelements in crossing relation.

The house or consumers wires 23 are con-' nected to the terminal posts 4and to the binding post 19-0f the elements 17. This arrangement, as willbe evident to one skilled in the art enables the lines 23 to be coupledup so as to use either 110 V or 220- V or 440 V current by means ofstandard or special transformers constructed to suit, as above stated.

By means of this arrangement of the cutout structure in connection withthe transformer, it will be seen that the current flowing from thesecondary windings of the transformer through the wiring 23 will passthrough the resistance elements, heating the same. These elements andthe block 10, however, are so designed that under normal conditions theheat generated and imparted to the block is insuflicient to melt orappreciably soften the plug, and consequently the contact plates 5 aremaintained in engagement with the contacts 2 and the circuit from thetransformer to the wiring 23 remains closed.

/ When an overload or short circuit is present in the wiring 23 however,the heat generatcd by the elements 17 is greater. T herefore, after thisoverloading condition has continued for a certain length of time, theblock 10 will be heated to a considerable degree above its normal heat,causing the plug 12 to be so softened that the strength of the springs 9will be suflicient to shear the sides of the plug around the rim of theoverhanging orifice 16 of the retaining plate. This of course will causethe plug to be drawn out of its socket in the block and there is thennothing to hold the bar 7 to the other parts of the structure. Thesprings are then free to act, first pushing the bar against the nuts 8and then causing the bar and all parts corinected thereto to jump clearof the remainder of the structure and the bridging of the contacts 2 tobe broken. T he circuit to the transformer is thus broken before anyharm is done. i

This breaking of the circuit, however, does not take place immediatelyupon the short circuit being had as is the case with ordinary fuses,since it takes an appreciable time for the block to heat sufficiently tocause the plug to soften to the extent necessary to cause it to shearpast the retaining plate. \Vhen the plug is thus sheared off and thecircuit broken it is only necessary to remove the retaining plate 15,mount another plug on the stem 13, press down the new plug into thesocket and replace the plate, the contact plates then of courseautomatically resuming their bridging engagement with the contacts. Thisplug. or at most the plug and its stem are the only new parts to besupplied after the structure has functioned in a protecting manner, andthe cost of which parts is very little as will be evident.

It will be noted that the springs have a double function, serving notonly to yieldably press the contact plates against the contacts 2, butalso acting to throw the bar 7 andconsequently said contact plates,clear of the structure when the block is sheared off.

The cut-out point in relation to the time and heat necessary may bevaried by changing the lossin the heater elements; the size and shape ofthe block; the temperature of the melting point of the plug; and byadjusting the nuts on the plug stem so that the strength of the springs,which maintains the plug in shearing engagement with the retainingplate, is altered. It will be also noted that the plug is mounted andused not as a solder, or as a current carrying element but as a sectionin shear.

It will also be seen that when the shearing action occurs, though theshearing movement itself may take place slowly, the final separation ofthe contact plates 5 from the contacts 2 will be almost instantaneousdue to the sudden release of the springs when the plug is fully shearedoff. There is therefore no arcing at the contacts at the instant ofbreaking of the circuit.

The above described apparatus is suitable for ordinary currentcapacities. For small sizes and capacities, the plates 5 would be asshown, while for larger capacities, said plates should be of laminatedconstruction. For very heavy duty, however, I preferably employ thestructure shown in Eig. 5. In this modified form of the device theholding plug stem 13 is connected to one end of a lever 24 which ispivoted at its opposite end on the base panel 1. Intermediate its endthis lever has a cross bar 7 mounted thereon, which bar supports theswitch plate stems 6. The functioning of this structure is substantiallythe same as that above described as will be evident, with the exceptionthat the lever being pivoted onto the panel does not ever becomeactually disassociated from the panel.

In both forms of the device, the panels are intended to be mounted in avertical position, so that when the circuit is broken the switch orcontact plates of either type will be positively thrown clear f thecontacts.

From the foregoing description it will be readily seen that I haveproduced such a device as substantially fulfills the objects of theinvention as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of the device, still in practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention, as defined by the appended claims.

Having thus described my invention what ary winding of a transformer inwhich said contacts are interposed, and means actuated by the heatgenerated by said elements to permit said supporting means to move awayfrom the contacts when the elements are heated to a predetermined degreeand for a predetermined period of time.

2. A transformer cut-out including a pair of spaced contact members, aplate to engage and bridge the same, supporting means for the plate, asoft-metal plug, means connecting said plug to the supporting means,means arranged. in connection with the plug to normally retain the samein shearing relation therewith, means acting on the supporting means,tending to move the same away from the contacts and placing a shearingstrain on the plug, and means for heating and softening the plug, saidheating means and contacts being adapted to be interposed in the circuitfrom the secondary winding of a transformer.

3. A transformer.cutout including a pair of spaced contact members, aplate to engage and bridge the same, supporting means for the plate, asoft-metal plug, means connecting said plug to the supporting means, arelatively hard block in the outer face of which said plug is mounted,an orificed member mounted on the outer face of the block; the orificealining with and overhanging the side edges of the plug, means acting onthe supporting means to move the same away from the block, and heatingelements associated with the block and adapted to be interposed in thecircuit from the secondary'winding of a transformer and in which circuitthe contacts are. also interposed.

4. A transformer cut-out including a pair of spaced contact members, aplate to engage and bridge the same, a stem projecting from the plate inthe direction opposite to the contacts, a bar through which thestem isslidable, a compression spring between the plate and bar, another stemsecured to and depending from the bar, a soft metal plug fixed on saidother stem, a retaining plate fixed with respect to the contacts anddisposed between the plug and bar, said retaining plate having anorifice alined with and overhanging the sides of the plug, and electricmeans for heating the plug under certain conditions sufficient to causethe plug to shear past the retaining plate with the pull of the springthereon, said contactsand heating means being adapted to be interposedin the circuit 'from the secondary winding of a trans-.

former. p 7

5. A transformer cut-out including a pair of spaced contact members, aplate to engage and bridge the same, a'stem projecting from the plate inthe direction Opposite to the contacts, a bar through which the stem isslid-- able, a compression spring secured to and depending from the bar,a soft metal plug fixed 10 on said other stem, a retaining platedisposed betweenthe plug and bar and having an orifice overhanging theside edges of the plug, a relatively hard block fixed with respect tothe contacts, the plate being fixed on the block and the latter having asocket in which the plug is disposed; and electric heating meansarranged in connection with the block to heat the same, said contactsand heating means being adapted to be interposed in the circuit from thesecondary winding of a transformer. a I r In testimony whereof I affixmy signature.

RICHARD W. SHOEMAKER. J

